QDBusMetaTypeId: don't cache the result of qMetaTypeId<>() in static ints

There's not much point in caching the result of qMetaTypeId<>,
because it's already internally memoised.

In addition, the code that initialised the static int caches wasn't
protected against concurrent access under the assumption that the
operations performed were thread-safe.

That is true for most of them, but not for the stores to the static ints,
which race against each other:

   // Thread A               // Thread B
   r1 = initialized /*=false*/
                             r1 = initialized /*=false*/
   r2 = qMetaTypeId<...>();
                             r2 = qMetaTypeId<...>();
   message = r2;             message = r2; // race, ditto for all other ints

To fix, turn the ints into inline functions that just call the respective
qMetaTypeId<>() function.

Change-Id: I5aa80c624872c3867232abc26ffdcde70cd54022
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 42 insertions, 7 deletions

diff --git a/src/dbus/qdbusmetatype_p.h b/src/dbus/qdbusmetatype_p.h
index 8239657232..8814408cc1 100644
--- a/src/dbus/qdbusmetatype_p.h
+++ b/src/dbus/qdbusmetatype_p.h
@@ -55,21 +55,56 @@
 
 #include <qdbusmetatype.h>
 
+#include <qdbusmessage.h>
+#include <qdbusargument.h>
+#include <qdbusextratypes.h>
+#include <qdbuserror.h>
+#include <qdbusunixfiledescriptor.h>
+
 QT_BEGIN_NAMESPACE
 
 struct QDBusMetaTypeId
 {
-    static int message;         // QDBusMessage
-    static int argument;        // QDBusArgument
-    static int variant;         // QDBusVariant
-    static int objectpath;      // QDBusObjectPath
-    static int signature;       // QDBusSignature
-    static int error;           // QDBusError
-    static int unixfd;          // QDBusUnixFileDescriptor
+    static int message();         // QDBusMessage
+    static int argument();        // QDBusArgument
+    static int variant();         // QDBusVariant
+    static int objectpath();      // QDBusObjectPath
+    static int signature();       // QDBusSignature
+    static int error();           // QDBusError
+    static int unixfd();          // QDBusUnixFileDescriptor
 
     static void init();
 };
 
+inline int QDBusMetaTypeId::message()
+#ifdef QT_BOOTSTRAPPED
+{ return qDBusRegisterMetaType<QList<QDBusUnixFileDescriptor> >() + 1; }
+#else
+{ return qMetaTypeId<QDBusMessage>(); }
+#endif
+
+inline int QDBusMetaTypeId::argument()
+{ return qMetaTypeId<QDBusArgument>(); }
+
+inline int QDBusMetaTypeId::variant()
+{ return qMetaTypeId<QDBusVariant>(); }
+
+inline int QDBusMetaTypeId::objectpath()
+{ return qMetaTypeId<QDBusObjectPath>(); }
+
+inline int QDBusMetaTypeId::signature()
+{ return qMetaTypeId<QDBusSignature>(); }
+
+inline int QDBusMetaTypeId::error()
+#ifdef QT_BOOTSTRAPPED
+{ return qDBusRegisterMetaType<QList<QDBusUnixFileDescriptor> >() + 2; }
+#else
+{ return qMetaTypeId<QDBusError>(); }
+#endif
+
+inline int QDBusMetaTypeId::unixfd()
+{ return qMetaTypeId<QDBusUnixFileDescriptor>(); }
+
 QT_END_NAMESPACE
 
 #endif